Mountain protected areas provide a range of ecosystem services including conserving biodiversity, while often providing recreation and tourism opportunities. Unfortunately, tourists and pack animals used to transport equipment can damage sensitive alpine vegetation particularly when they leave trails. This study assessed the impacts of disturbance from off trail use on alpine vegetation in a popular park in the Andes. The effect of different levels of disturbance as well as abiotic factors on alpine steppe vegetation was assessed using generalized linear models and ordinations in 91 plots (20 m2) in the popular Horcones Valley that is used to access remote areas in Aconcagua Provincial Park in Argentina. Disturbance off trails resulted in declines in the cover of native plants, including the endemic shrub Adesmia aegiceras but increases in the cover of herbs including the non-native Convolvulus arvensis. Increased disturbance was associated with shifts from stress tolerant species to ruderal plants characterized by more acquisitive traits, including shorter plants with greater Specific Leaf Area. The research demonstrates the severity of impacts from off trail trampling including how trampling favours some species with specific traits over others and why it is important to limit off track use in areas of high conservation value.